Through an open records request, The Times obtained a database of more than 2.6 million parking citations issued in 2012 from the Los Angeles Department of Transportation. Using mapping software, reporters were able to plot 87% of the unique addresses where tickets were written.

Reporters mapped street-sweeping parking tickets to the neighborhood level as defined by the Times' Mapping L.A. boundaries. Once matched to the respective neighborhoods, a regression analysis found that population density was the strongest predictor of street-cleaning ticket volume when socioeconomic factors were taken into account.

Last year, the L.A. transportation department provided a database of 2012 citations at no cost. This year, a reporter filed a public records request for similar information from 2013, but a department spokesman said the data would cost $3,200 to produce. The Times choose to not pay the fee.